Flow injection determination of hydrazine with fluorimetric detection

A spectrophotometric flow injection system is described for the determination of hydrazine, involving oxidation of hydrazine by thallium(III) with concomitant formation of thallium(I). The optimum analytical conditions have been established. The linear range for hydrazine is 25-500 ng ml(-1) with a detection limit of 20 ng ml(-1). The sampling frequency is 40+/-5 samples h(-1). The relative standard deviation for 100, 250 and 500 ng ml(-1) is 3.5, 2.6 and 1.8%, respectively. The method has been applied to the determination of hydrazine in water.     

Flow injection fluorimetric determination of beta-estradiol using a molecularly imprinted polymer

The steroidal compound 17beta-estradiol (E2) is a major estrogen now widely studied because of its potential endocrine disruption effects. The present paper describes a simple, rapid, flow injection (FI) method for the fluorimetric determination of beta-estradiol involving a molecularly imprinted polymer (MIP) packed into a microcolumn. Microwave-assisted extraction, a relatively new technique, was used to help remove the template from the MIP; this improved extraction efficiency. The optimization of the FI parameters and the intrinsic fluorescence of beta-estradiol allowed its direct determination without a derivatization step. When the possible interference of other estrogens was examined, the system displayed excellent specificity for beta-estradiol; no response to the natural estrogens estrone and estriol and the xenoestrogen bisphenol A was recorded. Under optimum experimental conditions, linear calibration graphs were obtained from 4 to 80 microg L(-1) with a detection limit of 1.12 microg L(-1).     

Flow injection determination of methamidophos using online photo-oxidation and fluorimetric detection

A photochemical method for the determination of methamidophos using a flow injection system is proposed. The method is based on the rapid decomposition of methamidophos in the presence of peroxydisulphate upon irradiation with UV light. The phosphate generated in the photochemical process is made to react with molybdate in dilute nitric acid to form phosphomolybdic acid, which oxidises thiamine to thiochrome. The thiochrome can then be fluorimetrically monitored at 440 nm with excitation at 375 nm. The method shows a linear range between 14 and 1400 ng ml(-1) with a limit of detection of 1.7 ng ml(-1). The repeatability was 0.3% expressed as relative standard deviation (n=10) and the reproducibility, studied on five different days, was +/-3%. The sample throughput was 70 injections per h. The reliability of the method for routine analysis of water and vegetable samples is demonstrated.     

Flow injection fluorimetric determination of thiamine and copper based on the formation of thiochrome

The reaction, involving the oxidation of thiamine by copper(II) in basic solutions to fluorescent thiochrome, has been adapted to the determination of thiamine by flow-injection analysis. Linear calibration graphs are obtained between 0.30 and 6.02 mug/ml with a sampling rate of 50 samples/hr and a relative standard deviation of 0.53%. This reaction has also been adapted to the determination of copper(II) over the range 0.5-5.0 mug/ml. The applicability of both methods for determination of thiamine and copper is demonstrated by investigating the effect of potential interferences and by the analysis of real samples (pharmaceuticals for thiamine and ores and alloys for copper).     

Flow injection fluorimetric determination of L-dopa and dopamine based on a photochemical inhibition process

An automatic procedure has been developed for the determination of L-dopa and dopamine. It is based on the strong inhibition of the photochemical reaction between thionine blue and ethylenediamine-tetraacetic acid by these catecholamines. The proposed flow-injection method allows for the fluorimetric determination of L-dopa in the range of 1.9–98 μg mL⁻¹ and that of dopamine in the range of 1.9–75 μg mL⁻¹ with a sampling frequency of 35 samples h⁻¹. The method was applied successfully to the determination of dopamine in pharmaceutical preparations.     

Flow injection method for the fluorimetric determination of Zn with 8-(benzenesulphonamido) quinoline

The development of a fluorimetric method for the determination of zinc, based on the fluorescence of the zinc-8-(benzenesulphonamido) quinoline chelate in a micellar medium of sodium dodecylsulfate, is reported. The detection limit is 0.2 g l^–1, the working range is 0.5–700 g l^–1, and the sample throughput is 145 h^–1. The method was evaluated for the determination of zinc in food samples.A batch procedure for the simultaneous determination of zinc and cadmium, based on the synchronous and derivative spectra, is also proposed.     

Sequential injection fluorimetric determination of Sn in juices of canned fruits

The present work describes the development of a fast and robust sequential injection fluorimetric procedure for the determination of Sn in juices of canned fruits. The developed automatic methodology is based on the complexation of Sn with 8-hydroxyquinoline-5-sulfonic acid (HQSA) to form a fluorimetric product (λ_exc = 354 nm; λ_em = 510 nm). The influence of dimethylsulfoxide (DMSO) and cetylpyridinium bromide (CPB) on the sensitivity of the fluorimetric determination was evaluated.Linear calibration plots were obtained for Sn concentrations between 1 and 10 mg L⁻¹, with a detection limit of 0.38 mg L⁻¹. In each analytical cycle 0.006 mg of HQSA and 0.47 mg of CPB were consumed and 1.5 mL of effluent was generated.The developed methodology was applied to the determination of Sn in juices of canned fruits and the results complied with those furnished by an electrothermal atomic absorption spectrometry comparison procedure, with relative deviations lower than 5.2%.The automatic procedure exhibited good precision (R.S.D. < 1.4%) and the sampling rate was about 70 determinations per hour.     

Rapid and selective determination of ammonium by fluorimetric flow injection analysis

Selective and sensitive procedures for the determination of ammonium in river water and diluted urine were developed by using flow injection analysis equipment. The methods are based on the derivatization of ammonia with o-phthaldehyde (OPA) and thioglycolate under alkaline conditions. The formed isoindole derivative is detected fluorimetrically at an excitation wavelength of 415 nm and an emission wavelength of 485 nm. The derivatization only takes 15 to 20 s at room temperature to achieve the maximum sensitivity. The optimized OPA reagent shows a surprisingly high selectivity for ammonium in the presence of many primary amines. With respect to the analysis of turbid and fluorescent sample solutions the selectivity can be improved by separating the ammonia through a microporous membrane from the OPA reagent. Without this separation step ammonia can be detected in the range between 0.05 and 100 microM with excellent linearity. After the insertion of an optimized membrane separation cell ammonia can be determined in the linear range between 0.2 microM and 20 mM.     

Rapid and selective determination of ammonium by fluorimetric flow injection analysis

Selective and sensitive procedures for the determination of ammonium in river water and diluted urine were developed by using flow injection analysis equipment. The methods are based on the derivatization of ammonia with o-phthaldehyde (OPA) and thioglycolate under alkaline conditions. The formed isoindole derivative is detected fluorimetrically at an excitation wavelength of 415 nm and an emission wavelength of 485 nm. The derivatization only takes 15 to 20 s at room temperature to achieve the maximum sensitivity. The optimized OPA reagent shows a surprisingly high selectivity for ammonium in the presence of many primary amines. With respect to the analysis of turbid and fluorescent sample solutions the selectivity can be improved by separating the ammonia through a microporous membrane from the OPA reagent. Without this separation step ammonia can be detected in the range between 0.05 and 100 μM with excellent linearity. After the insertion of an optimized membrane separation cell ammonia can be determined in the linear range between 0.2 μM and 20 mM.     

流动注射化学发光分析法测定利福平

在酸性条件下,KMnO4能氧化利福平产生弱化学发光,并且,利福平能极大的增敏Na2SO3-KMnO4体系的化学发光信号。基于此,结合流动注射技术,建立了测定利福平的新方法。在优化的条件下,利福平在5.0×10-8g/mL~1.0×10-5g/mL范围内与化学发光强度呈良好的线性关系,检出限为3×10-8g/mL。对2.0×10-6g/mL的利福平进行11次平行测定,相对标准偏差为2.6%。该法用于胶囊和滴眼液中利福平的测定,并初步探讨了该化学发光反应机理。     

流动注射化学发光法测定己烯雌酚

基于己烯雌酚对鲁米诺与高碘酸钾在碱性介质中反应产生的化学发光信号有较强的增敏作用,建立了测定己烯雌酚的流动注射化学发光分析法。己烯雌酚质量浓度在13．4—1340μg／L范围内与化学发光强度呈良好的线性关系,检出限（3d）为4μg／L;对26．8μg／L己烯雌酚进行11次平行测定,相对标准偏差（RSD）为1．4％。该法已用于药物制剂中己烯雌酚的测定。     

流动注射化学发光法测定吗丁啉

在碱性条件下 ,H2 O2 氧化鲁米诺产生化学发光 ,吗丁啉对该体系的化学发光具有显著的增敏作用。基于此 ,建立了一种直接测定吗丁啉的流动注射化学发光分析法。该方法的线性范围在 1 .0× 1 0 -6～ 3.0× 1 0 -8g mL ,检出限 ( 3σ)为 5 .0× 1 0 -9g mL ,相对标准偏差为 2 .9% (n =1 1 ) ,已用于吗丁啉片剂及血清中吗丁啉的分析。     

高锰酸钾-亚硫酸钠-氨基比林化学发光体系的研究

采用流动注射技术,研究了高锰酸钾-亚硫酸钠-氨基比林体系的化学发光行为,对影响化学发光强度的诸因素进行了实验和探讨,建立了化学发光法测定氨基比林的新方法.方法的检出限为3×10-8 g/mL,线性范围为1.0 ×10-7～8.0×10-5 g/mL.对4.0×10-6 g/mL的氨基比林进行11次平行测定,得方法的相对标准偏差为1.7%.方法用于药剂中氨基比林含量的测定,结果与分光光度法测得值一致.     

流动注射化学发光法测定阿莫西林

在碱性介质中,铁氰化钾能够氧化阿莫西林产生微弱的化学发光,Na2SO3对该体系有较强的增敏作用,据此,结合流动注射技术,建立了测定阿莫西林的新方法.阿莫西林在5.0×10-8～2.0×10-5 g/mL范围内与化学发光强度呈良好的线性关系,检出限为3×10-8 g/mL,对2.0×10-6 g/mL的阿莫西林进行11次平行测定,相对标准偏差为1.5%.本法已用于胶囊中阿莫西林的测定,并初步探讨了该化学发光反应的机理.     

流动注射化学发光法测定阿莫西林

在碱性介质中 ,阿莫西林抗生素对鲁米诺 KMnO4化学发光反应有增敏作用 ,据此建立了微量快速测定阿莫西林的流动注射化学发光分析法。该法线性范围为 1 .0× 1 0 -7～ 5 .0× 1 0 -5g mL ,检出限为 3.0× 1 0 -8g mL ;对 1 .0× 1 0 -6g mL阿莫西林 1 1次平行测定 ,其相对标准偏差为 1 .7%。此法已用于阿莫西林胶囊中阿莫西林的测定。     

流动注射化学发光分析法测定卡马西平

基于酸性条件下溴化钠对NaIO4-H2O2-卡马西平化学发光反应体系具有明显的增敏作用,结合流动注射技术建立了一种测定卡马西平的新方法.在优化的实验条件下,方法的线性范围为1.0×10-9～8.0×10-6g/mL,检出限为3.6×10-10g/mL,相对标准偏差为2.5％(c=2.0×10-7g/mL,n=11),回收率在98.4％～100.6％间.     

流动注射化学发光法测定呋塞米

在酸性条件下呋塞米对Ce(Ⅳ)-Na_2SO_3弱化学发光体系具有很强的增敏作用,据此建立了流动注射化学发光法测定呋塞米的新方法.该法测定呋塞米的线性范围为0.01～1.0 mg/L,检出限为4×10~(-3)mg/L(3σ),RSD为2.2%(n=11,ρ=0.2mg/L),回收率为95%～105%.该法已应用于片剂和针剂中呋塞米含量的测定.     

Flow injection chemiluminescence determination of medazepam

A new flow injection chemiluminescence method for the assay of medazepam is explored. The method involves the use of permanganate in sulfuric acid for the oxidation of medazepam with the emission of chemiluminescence detected by a photomultiplier tube. A simplex procedure was employed for optimising the conditions for high sensitivity detection, which were found to be 1.03 × 10^–3 mol L^–1 permanganate, 0.153 mol L^–1 sulfuric acid and 3.43 mL min^–1 flow rate. The linear calibration range was 3.7 × 10^–5 to 1.7 × 10^–3 mol L^–1. The detection limit (3σ) and the sample throughput were 1.85 × 10^–5 mol L^–1 and 100 per hour, respectively. The relative standard deviation for 5 replicate determinations of 1.9 × 10^–4 mol L^–1 medazepam was 0.15%. Common excipients (starch, glucose, maltose, lactose) used in pharmaceutical preparations had no effect. Received: 2 February 1998 / Revised: 20 May 1998 / Accepted: 25 May 1998     

Flow injection chemiluminescence determination of paracetamol

A simple chemiluminometric method using flow injection has been developed for the determination of paracetamol (acetaminophen), based on the chemiluminescence produced by the reduction of tris(2,2′-bipyridyl)ruthenium(III). The latter is obtained by oxidation of tris(2,2′-bipyridyl)ruthenium(II) by potassium permanganate in dilute sulphuric acid in the presence of paracetamol. A standard or sample solution was injected into the ruthenium(II) stream (flow rate 1.5 ml min⁻¹) which was then merged with potassium permanganate in dilute sulphuric acid stream (flow rate 0.5 ml min⁻¹). The chemiluminescence intensity is enhanced by the presence of manganese(II) ions. Under the optimum conditions, a linear calibration graph was obtained over the range of 0.3-50.0 μg ml⁻¹ and the detection limit was 0.2 μg ml⁻¹ (s/n = 3). The relative standard deviation of the proposed method calculated from 20 replicate injections of 5.0 μg ml⁻¹ paracetamol was 1.1%. The sample throughput was 90 h⁻¹. The method was successfully applied to the determination of paracetamol in commercial pharmaceutical formulations.     

Flow injection spectrophotometric determination of nitrite

4-Nitroaniline, which gives intensely yellow solution on dissolution in dilute hydrochloric acid, has been found to react with nitrite almost instantaneously in acidic medium yielding a colourless product that has been identified as 4-nitrophenyl diazo cation. The measurement of decrease in colour intensity suggested a new, simple and one-step reaction procedure that has been used for the reversed flow injection determination of 5microg-5 mg/l. NO(2)-N. The limit of detection has been found to be 2 microg/l. NO(2)-N. A number of species such as copper(II) and lead(II), which interfere in other spectrophotometric procedures, do not affect the results. The method has been applied to determine nitrite in natural waters when the %RSD was in the range 1.8-3.5%.